Java vs. C#

namespace vs. package

Java
 
Packages are used to organize files or public types to avoid 
type conflicts. 
Package constructs can be mapped to a file system.


System.Security.Cryptography.AsymmetricAlgorithm aa;
may be replaced:
import System.Security.Crypography; 
class xxx { ...
AsymmetricAlgorithm aa;

There is no alias for packages.
You have to use import statement 
or fully-qualified name to 
mention the specific type.




pacakge N1.N2;
    class A {}
    class B {}
or
package N1.N2;
   class A {}

//another source file
package N1.N2;
   class B {}
   
package cannot be nested.
One source file can only 
have one package statement.

C#
 
Namespaces are used to organize programs,
both as an "internal" organization system for a program, 
and as an "external" organization system.


System.Security.Cryptography.AsymmetricAlgorithm aa;
may be replaced:
using System.Security.Crypography; 
AsymmetricAlgorithm aa;

Alternatively, one could specify an alias 
for the the namespace, eg 

using myAlias = System.Security.Crypography; 
and then refer to the class with 

myAlias.AsymmetricAlgorithm 


namespace N1.N2
{
    class A {}
    class B {}
}
or
namespace N1
{
    namespace N2
    {
        class A {}
        class B {}
    }
}